Aluminum hydroxide has a variety of alternative names such as aluminum hydrate, aluminum trihydrate etc., but is commonly referred to as ATH. ATH particles find use as a filler in many materials such as, for example, plastics, rubber, thermosets, papers, etc. These products find use in diverse commercial applications such as wire and cable compounds, conveyor belts, thermoplastics moldings, wall claddings, floorings, etc. ATH is typically used to improve the flame retardancy of such materials and also acts as a smoke suppressant.
Methods for the synthesis of ATH are well known in the art. For example, see EP 1 206 412 B1 describes the production of fine precipitated aluminum hydroxide grades wherein a pregnant liquor obtained from the Bayer process is seeded with bayerite crystals. By using controlled conditions during crystallization, tailor made ATH grades with consistent product qualities can be produced. The ATH grades are typically distinguished by two important characteristics, the median particle size, commonly referred to as d50, and the specific surface, commonly referred to as the BET specific surface area, and these two characteristics are major criteria to select an ATH for a specific application.
However, ATH's are not selected solely on their d50 and/or BET specific surface areas. To the contrary, ATH's are also selected based on the compounding performance of the ATH-containing resin, and the demand for better compounding performance has increased. The compounding performance of an ATH-containing resin is generally determined by viewing the power draw on the motor of the compounding machine used in compounding the ATH-containing resin. Less variations of the power draw on the motor of the compounding machine translates to less wear on the compounder engine, better compounded resins, and higher throughputs of the ATH-containing resin during compounding.
Thus, because there is a demand for higher throughputs in the compounding of ATH-flame retarded resins and the performance of the ATH-flame retarded synthetic resin is a critical attribute that is linked to the ATH, compounders would benefit from, and thus there is a demand for, an ATH which, during compounding, would allow for higher throughputs in compounding machines like Buss Ko-kneaders, twin-screw extruders or other suitable machines.